Conventional systems for generating an audible signal in a motor vehicle (for example, as described in U.S. Pat. No. 2,283,659) include a control system which provides a sound warning signal of relatively low volume or relatively short duration suitable for city driving and a signal of longer duration having a higher volume for highway driving. This control system has two horns of which only one horn is active in city traffic, while both are active in highway traffic. The horns are controlled by either an activation of an air fan for grounding a heating coil, a heat exhaust temperature sensor, an accelerator pedal sensor or a brake pedal sensor.
Another conventional system for generating an audible signal in the motor vehicle is described in U.S. Pat. No. 5,012,221. This system is an audible warning system used in emergency vehicles and provides different selectable sounds to indicate various levels of urgency. In particular, the system is coupled to a speed sensor (or to an electromagnetic device) so that the output of an audible waveform generator is controlled by the speed sensor. Therefore, an amplitude and frequency of sound are modified based on an output of the speed sensor or an output of the electromagnetic device.
The conventional systems for generating an audible signals in a motor vehicle do not, however, provide any audible indication whenever a dangerous situation occurs or is about to occur. It is therefore an object of the present invention to provide a device to warn motor vehicles of a possible impending danger when another motor vehicle is performing an evasive maneuver. It is also an object of the present invention for such a device to include an audible horn with a variable output that modifies a pitch and/or volume of emitted audible signal during city driving (e.g., below 25 mph), normal driving (e.g., 25-50 mph) and highway driving (e.g., above 50 mph).